Effects of RGMc on BMP2 and BMP6-mediated Gene Expression in Hep3B Liver Cells
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE20671 | GEO | 2010/06/15
SECONDARY ACCESSION(S): PRJNA124929
REPOSITORIES: GEO
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Project description:Mutations in repulsive guidance molecule c (RGMc) / hemojuvelin (HJV) cause juvenile hemochromatosis, an aggravated iron overload disorder that presents early in life. Patients with juvenile hemochromatosis, and RGMc knockout mice, have diminished expression of the key iron-regulatory peptide, hepcidin. This suggests that RGMc plays a critical role in the regulation of iron homeostasis; however the mechanisms of RGMc actions are unknown. Recent studies have shown that RGMc directly binds to the growth factors, bone morphogenetic protein 2 and 6 (BMP2 and BMP6), and it is possible that this interaction regulates aspects of iron metabolism. We used microarrays to examine the effects of RGMc on BMP2- and BMP6-mediated gene expression. In our experimental model we treated Hep3B liver cells that had been serum starved for 16 hours as follows: (1) un-treated, (2) BMP2, (3) BMP2 + 10-fold molar excess of Noggin (a potent BMP2 inhibitor), (4) BMP2 + 20-fold molar excess of RGMc, (5) BMP6, (6) BMP6 + 10-fold molar excess of Noggin, (7) BMP6 + 20-fold molar excess of RGMc. Binding was allowed to proceed for BMP and Noggin or RGMc for 3 hr at 20°C prior to treatment of Hep3B cells. Treatment time was 4 hr at which cells were collected for RNA isolation.
2010-06-23 | E-GEOD-20671 | biostudies-arrayexpress
Project description:Microvascular endothelial cells (EC) display a high degree of phenotypic and functional heterogeneity among different organs. Organ-specific EC control their tissue microenvironment by angiocrine factors in health and disease. Liver sinusoidal EC (LSEC) are uniquely differentiated to fulfil important organ-specific functions in development, under homeostatic conditions, and in regeneration and liver pathology. Recently, Bmp2 has been identified by us as an organ-specific angiokine derived from LSEC. To study angiocrine Bmp2 signaling in the liver, we conditionally deleted Bmp2 in LSEC using EC subtype-specific Stab2-Cre mice. Genetic inactivation of hepatic angiocrine Bmp2 signaling in Stab2-Cre;Bmp2fl/fl (Bmp2LSECKO) mice caused massive iron overload in the liver, and increased serum iron levels and iron deposition in several organs similar to classic hereditary hemochromatosis. Iron overload was mediated by decreased hepatic expression of hepcidin, a key regulator of iron homeostasis. Thus, angiocrine Bmp2 signaling within the hepatic vascular niche represents a constitutive pathway indispensable for iron homeostasis in vivo that is non-redundant with Bmp6. Notably, we demonstrate that organ-specific angiocrine signaling is essential not only for the homeostasis of the respective organ, but also for the homeostasis of the whole organism.
2017-01-31 | GSE90506 | GEO
Project description:Iron induces hepcidin by activating bone morphogenetic protein (BMP)6-SMAD signaling. Liver endothelial cells (LECs) produce BMP6, but the molecular mechanisms are incompletely understood. To address this, we performed proteomics and RNA-sequencing on LECs from iron-adequate and iron-loaded mice. Gene set enrichment analysis identified transcription factors activated by high iron, including Nrf-2, which was previously reported to contribute to BMP6 regulation, and proto-oncogene c-Jun (encoded by Jun). Jun knockdown blocked Bmp6, but not Nrf-2 pathway, induction by iron in LEC cultures. Moreover, chromatin immunoprecipitation of mouse livers showed iron-dependent c-Jun binding to predicted sites in Bmp6 regulatory regions. Finally, c-Jun inhibitor blunted induction of Bmp6 and hepcidin, but not Nrf-2 activity, in iron-loaded mice. However, Bmp6 expression and iron parameters were unchanged in endothelial Jun knockout mice. Our data suggest that c-Jun participates in iron-mediated BMP6 regulation independent of Nrf-2, though the mechanisms may be redundant and/or multifactorial.
2023-12-28 | PXD039830 | Pride
Project description:Background & Aims: Although hepcidin expression was shown to be induced by the BMP signaling pathway, it is not yet known how iron regulates hepcidin and which of the BMP molecules is the endogenous regulator of iron homeostasis in vivo. We therefore assessed liver transcription profiles of mice fed an iron-deficient or an iron-enriched diet and looked for genes that were regulated similarly to hepcidin in that context. Methods: Genome-wide liver expression profiles of mice of the B6 and D2 genetic backgrounds subjected to iron-deficient, -balanced, or -enriched diets were obtained using Agilent Whole Genome microarrays. Real-time quantitative-PCR and western-blots were used to confirm microarray results and compare gene expression variations induced by secondary iron deficiency or iron overload with those consecutive to Smad4 or Hamp1-deficiency. Results: Among 1419 transcripts significantly modulated by the dietary iron content, four were regulated similarly to the hepcidin genes Hamp1 and Hamp2. They are coding for Bmp6, the regulator of Bmp/Smad signal transduction Smad7, the negative regulator of basic helix-loop-helix (bHLH) proteins Id1, and a protein with a bHLH domain, Atoh8. The iron overload developed by Smad4 and Hamp1-deficient mice also increased Bmp6 transcription. Body iron stores influence Smad1/5/8 phosphorylation and, as shown by analysis of mice with liver-specific disruption of Smad4, the binding partner for the receptor-activated Smads is necessary for activation of Smad7, Id1, and Atoh8 transcription by iron. Conclusions: Liver expression of Bmp6, Smad7, Id1, and Atoh8 is regulated by body iron stores and may participate in hepcidin regulation through the Bmp/Smad pathway. Keywords: response to dietary iron content
2008-07-07 | GSE10421 | GEO
Project description:Homeostatic adaptation to systemic iron overload involves transcriptional induction of bone morphogenetic protein 6 (BMP6) in liver sinusoidal endothelial cells (LSECs). BMP6 is then secreted to activate signaling to the iron hormone hepcidin (Hamp) in neighboring hepatocytes. To explore the mechanism for iron sensing by LSECs, we generated TfrcTek-Cre mice with endothelial cell-specific ablation of transferrin receptor 1 (Tfr1). We also used wild type mice to characterize LSEC-specific molecular responses to iron by single cell transcriptomics. TfrcTek-Cre animals tend to have increased liver iron content compared to Tfrcfl/fl controls but do not exhibit blunted Bmp6 or Hamp mRNA expression. They respond to dietary iron challenges with Bmp6 and Hamp induction, yet sometimes to levels slightly lower relative to liver iron load. We noted that liver Bmp6 and Hamp mRNA levels significantly correlated with serum non-transferrin bound iron (NTBI) that emerged following dietary iron loading in both TfrcTek-Cre and Tfrcfl/fl mice. High dietary iron triggered more profound alterations in the LSEC transcriptome of Tfrcfl/fl mice compared to holo-transferrin injection. These culminated in robust induction of Bmp6 and other nuclear factor erythroid 2-related factor 2 (Nrf2) target genes, as well as Myc target genes involved in ribosomal biogenesis and protein synthesis. Taken together, our data suggest that during systemic iron overload, LSECs internalize NTBI, which promotes oxidative stress and thereby transcriptionally induces Bmp6 via Nrf2. The contribution of Tfr1 and transferrin-bound iron to Bmp6 induction is minimal.
2022-12-21 | GSE215324 | GEO
Project description:BMP6 is an iron-sensing cytokine produced by liver sinusoidal endothelial cells (LSECs). The transcription factor NRF2 was proposed to induce Bmp6 expression in response to iron-triggered oxidative stress, and NRF2 knock-out mice were shown not capable of regulating Bmp6 in response to massive diet-imposed iron overload. However, LSEC Bmp6 expression levels in the hemochromatosis mouse model reflect hepatocytic, not endothelial iron content. Hence, it is not fully resolved how iron signals translate into alterations of Bmp6 mRNA levels. To further explore the mechanisms of Bmp6 regulation, we employed female mice aged 10-11 months that are hallmarked by hepatocytic, but not LSEC iron accumulation and decreased transferrin saturation, hinting at the absence of systemic iron overload. We found that LSECs of aged mice exhibit increased Bmp6 levels as compared to young controls, but do not show oxidative stress or a transcriptional signature characteristic of activated NFR2-mediated signaling in FACS-sorted LSECs. We further observed that primary murine LSECs derived from both wild-type and NRF2 knock-out mice induce Bmp6 in response to acute iron exposure. By analyzing RNA sequencing data of FACS-sorted LSECs from aged versus young mice, as well as upon acute injections of iron citrate in young mice, we identified ETS1 as a candidate transcription factor involved in Bmp6 regulation. By conducting siRNA-mediated knock-down and small-molecule treatments in primary LSECs, we show that Bmp6 transcription is regulated in an NRF2-independent manner via ETS1, which is activated downstream of p38 MAP kinase-mediated signaling. This knowledge expands the understanding of Bmp6 transcriptional control in both iron-triggered oxidative stress and under the conditions uncoupled to LSECs reactive oxygen species levels.
2024-01-25 | GSE235975 | GEO
Project description:BMP6 is an iron-sensing cytokine produced by liver sinusoidal endothelial cells (LSECs). The transcription factor NRF2 was proposed to induce Bmp6 expression in response to iron-triggered oxidative stress, and NRF2 knock-out mice were shown not capable of regulating Bmp6 in response to massive diet-imposed iron overload. However, LSEC Bmp6 expression levels in the hemochromatosis mouse model reflect hepatocytic, not endothelial iron content. Hence, it is not fully resolved how iron signals translate into alterations of Bmp6 mRNA levels. To further explore the mechanisms of Bmp6 regulation, we employed female mice aged 10-11 months that are hallmarked by hepatocytic, but not LSEC iron accumulation and decreased transferrin saturation, hinting at the absence of systemic iron overload. We found that LSECs of aged mice exhibit increased Bmp6 levels as compared to young controls, but do not show oxidative stress or a transcriptional signature characteristic of activated NFR2-mediated signaling in FACS-sorted LSECs. We further observed that primary murine LSECs derived from both wild-type and NRF2 knock-out mice induce Bmp6 in response to acute iron exposure. By analyzing RNA sequencing data of FACS-sorted LSECs from aged versus young mice, as well as upon acute injections of iron citrate in young mice, we identified ETS1 as a candidate transcription factor involved in Bmp6 regulation. By conducting siRNA-mediated knock-down and small-molecule treatments in primary LSECs, we show that Bmp6 transcription is regulated in an NRF2-independent manner via ETS1, which is activated downstream of p38 MAP kinase-mediated signaling. This knowledge expands the understanding of Bmp6 transcriptional control in both iron-triggered oxidative stress and under the conditions uncoupled to LSECs reactive oxygen species levels.
2024-01-25 | GSE235692 | GEO
Project description:Liver iron overload can induce hepatic expression of hepcidin and regulates iron metabolism. However, the mechanism of iron regulating iron metabolism remains known. Intracellular labile iron represents the nonferritin-bound, redox-active iron which is transitory and serves as a crossroad of cell iron metabolism. The role of intracellular labile iron played in iron metabolism has largely been elucidated. Here we show that intracellular labile iron of hepatocytes has dual function in iron metabolism. It can induce hepatocytes expressing hepcidin via ER stress induced transcription factors on the one hand, on the other hand stimulate BMP2 and BMP6 expression of liver sinusoidal endothelial cells (LSECs) though TNFα secreted by hepatocytes to further regulate iron metabolism. Blockade of TNFα could dysregulate the iron metabolism during iron overload. Our findings reveal the important role of intracellular labile iron in iron metabolism and represent a novel way to modulate iron metabolism during iron overload.
2023-05-03 | GSE186655 | GEO
Project description:Hepcidin, a peptide hormone that decreases intestinal iron absorption and macrophage iron release, is a potential drug target for patients with iron overload syndromes because its levels are inappropriately low in these individuals. Endogenous stimulants of Hepcidin transcription include bone morphogenic protein 6 (BMP) and interleukin-6 (IL-6) via effects on Smad4 or Stat3, respectively. We conducted a small-scale chemical screen in zebrafish embryos to identify small molecules that modulate hepcidin expression. We found that treatment with the isoflavone genistein from 28−52 hours post-fertilization in zebrafish embryos enhanced Hepcidin transcript levels as assessed by whole mount in situ hybridization and quantitative realtime RT-PCR. Genistein’s stimulatory effect was conserved in human hepatocytes: genistein treatment of HepG2 cells increased both Hepcidin transcript levels and Hepcidin promoter activity. We found that genistein’s effect on Hepcidin expression did not depend on estrogen receptor signaling or increased cellular iron uptake, but was impaired by mutation of either the BMP response elements or the Stat3 binding site in the Hepcidin promoter. RNA-sequencing of transcripts from genistein-treated hepatocytes indicated that genistein upregulated 68% of the transcripts that were upregulated by BMP6, however genistein raised the levels of several transcripts involved in Stat3 signaling that were not upregulated by BMP6. Chromatin-immunoprecipitation and ELISA experiments revealed that genistein enhanced Stat3 binding to the Hepcidin promoter and increased phosphorylation of Stat3 in HepG2 cells. CONCLUSION: Genistein is the first small molecule experimental drug that stimulates Hepcidin expression in vivo and in vitro. These experiments demonstrate the feasibility of identifying and characterizing small molecules that increase Hepcidin expression. Genistein and other candidate molecules may subsequently be developed into new therapies for iron overload syndromes. RNA-seq of HepG2 cells treated with DMSO 1%, BMP6 50 ng/ml, or genistein 10 micromolar. The numbers of biological replicates were 3, 2, and 3.
2015-08-13 | E-GEOD-40069 | biostudies-arrayexpress
Project description:Iron induces hepcidin by activating bone morphogenetic protein (BMP)6-SMAD signaling, which is critical for regulation of systemic iron homeostasis. High iron levels induce BMP6 production in liver endothelial cells, but the molecular mechanisms by which iron regulates BMP6 are incompletely understood. To address this, we performed RNA-sequencing on sorted liver endothelial cells from iron-adequate and iron-loaded mice.
2023-12-25 | GSE223871 | GEO